Spectrophotornetric investigation of the effect of β-cyclodextrin on the intramolecular cyclization reaction of catecholamines using rank annihilation factor analysis

The catalytic effect of beta-cyclodextrin (beta-CD) on the intramolecular cyclization reaction of catecholamines dopamine, methyldopa and levodopa after their oxidation with periodate was investigated spectrophotometrically using rank annihilation factor analysis (RAFA). The method was based on the effect of beta-CD concentration on the intramolecular cyclization reaction of the investigated catecholamines after their oxidation with potassium periodate. In order to perform RAFA, concentration profiles were calculated by optimizing the value of formation constant. The rank of original data matrix can be reduced by one by annihilating the information of the cyclization reaction in the absence of beta-CD. The rate constant for the reactions in the presence and absence of beta-CD was also determined. The best estimation of rate constant in the presence of beta-CD reduces the rank of the system to zero (noise level). The method was evaluated using synthetic data as well as experimental data and good results were obtained. (C) 2007 Elsevier B.V. All rights reserved.